Hole saws have been used by tradesman for drilling holes in paneling and the like for a number of years. In particular, electricians routinely use hole saws made from a tubularly-shaped saw blade to drill holes into electrical boxes made out of sheet metal to allow the ingress and egress of wires. After the hole is drilled, the slug which has been cut away, often remains lodged in the blade. Typically, these hole saws have at least one oval-shaped slot located on the side of the blade. The slot has a longitudinal axis that is parallel with the direction of drilling. This slot allows the user to slip a tool such as a screw driver into the slot behind the slug and force the slug out of the blade.
Many times, these hole saws are used when wires are already present within the box. This presents the danger that some of the wires already present will be cut or otherwise damaged during the hole cutting operation as the hole saw penetrates the panel. The cut or damaged wires present an electrical hazard once the wires are energized. As a result of this need, many hole saws have been developed to provide some means for limiting the penetration of the blade and therefore greatly reducing the possibility of damaging existing wiring within the electrical box.
One example of such a hole saw is disclosed by U.S. Pat. No. 1,522,102 which discloses a hand-powered boring drill whose drilling depth is controlled by a surface found on the bottom of the component that serves as the handle for the saw. This hole saw has disadvantages including that the stop requires four screws for attaching it to the hole saw, that the components are larger and more expensive than necessary, and that it is not adapted to be driven by an electrical drill as is now standard in the industry.
Another hole saw that has control of the drilling depth is described in U.S. Pat. No. 1,705,049 which discloses the use of a collar that is located about the circumference of the hole saw and is held in place by a locking member that impinges upon the outside circumference of the hole saw. However, this hole saw has the disadvantage that different sized collars for hole saws of different diameters are needed. This increases the cost and complexity of the overall system.
U.S. Pat. No. 5,205,685 discloses a hole saw that has a plastic or metal collar that is attached to the circumference of the hole saw by welding or adhesive. This hole saw also has the disadvantage that different sized collars are needed for different diameters which increases the cost and complexity of the overall system. Furthermore, the attachment of the stop collar is permanent, preventing removal when it is desired to allow deep penetration of the hole saw.
For these reasons, there still exists a need for a hole saw that has a depth stop that is easy to attach to the hole saw, that can be used with hole saws of differing diameters, that can be easily detached from the hole saw when desired, that allows the removal of a slug that is trapped within the inner circumference of the hole saw, and that can be inexpensively manufactured.